Air outlines bothsides of the wallof the stomach-asign of free airin the peritonealcavity

Pneumoperitoneum

Pneumoperitoneum - CT

CT scans on 2 different people show a small and large amount of free air in theperitoneal cavity which rises to the highest point (anteriorly with the personlying on their back) and is not contained within bowel

In the supine position, the fluid layers out posteriorly and produces ahaziness, especially near the bases (since the patient is actually semi-recumbent). In the erect position, the fluid falls to the bases.